Flat panel display has replaced heavy CRT display and is increasingly going deep into people's daily life. Currently, common flat panel displays comprise an LCD (liquid crystal display) and an OLED (organic light-emitting diode) display. The above flat panel displays have features of small volume, low power consumption, no radiation and etc., and have played a leading role in current flat panel display market.
An array substrate is an important constituting part of a display, wherein a thin film field effect transistor (TFT) array substrate is a type of array substrate that is currently used widely. For the TFT array substrate, a TFT switch is usually constituted by a gate electrode, a source/drain electrode and an active layer connected with the source/drain electrode, and a barrier layer is provided on the active layer. During forming the source/drain electrode, the barrier layer is used to prevent the active layer from being destroyed and then to improve the performance of the TFT switch. A data line is usually provided on the same metal layer with the source/drain electrode, a gate line and the gate electrode are provided on the same metal layer, referring to the schematic diagram of the section at the overlapping position of the data line and the gate line shown in FIG. 1, it comprises a data line 1, a gate line 2, a gate insulating layer 3 and a barrier layer 4. The gate insulating layer 3 and the barrier layer 4 usually use SiOx or SiOx/SiNx which have poor compactness, thus, the contact face between the gate insulating layer 3 or the barrier layer 4 and the adjacent metal layer has a bubble-shaped gap (for example, between the data line 1 and the barrier layer 4 shown in FIG. 1), and during etching the data line, as the contact face between the barrier layer and the metal forming the data line has the bubble-shaped gap, an etching liquid will enter the contact face between the barrier layer and the data line via the bubble-shaped gap, so that the data line is eroded and then cracked. This defect is especially serious at a slope position which can be understood as a position at the gate insulating layer or barrier layer where height changes and which usually corresponds to the position of the gate electrode or gate line (for example, the gradient position 5 at the overlapping position of the data line 1 and the gate line 2 shown in FIG. 1, and the height changes from low to high to form a slope).